With increasing development of personal computers, inkjet printing apparatuses are widely used as peripheral devices of personal computers. By means of the inkjet printing apparatus, the document file of a computer could be printed on many kinds of media (e.g. papers). FIG. 1 is a schematic perspective view illustrating an inkjet printing apparatus according to the prior art. As shown in FIG. 1, the inkjet printing apparatus 1 comprises an ink cartridge 10, multiple ink nozzles (not shown), a transmission mechanism 11, a paper input tray 12 and a paper output tray 13. The ink cartridge 10 is used for storing ink. The ink nozzles are disposed at the bottom of the transmission mechanism 11. The ink nozzles are moved by the transmission mechanism 11 such that ink could be ejected through the ink nozzles to be printed on any position of a blank paper P. The blank paper P is placed on the paper input tray 12. After an inkjet printing operation is performed, the paper P is exited to the paper output tray 13.
During the printing process of the inkjet printing apparatus 1, the blank paper P on the paper input tray 12 is fed into the inkjet printing apparatus 1 in a feeding direction Y and the transmission mechanism 11 is moved in a printing direction X. The printing direction X is perpendicular to the feeding direction Y. After the inkjet printing operation is completed, the paper P is exited to the paper output tray 13.
Generally, after the inkjet printing apparatus 1 is communicated with the computer and a print driver is installed, the inkjet printing apparatus 1 will perform a print testing operation. For performing the print testing operation, a first test image file stored in the computer is printed on a paper as a print test pattern. By visually examining the colors or image positions of the print test pattern, the user could discriminate whether the printing capability of the inkjet printing apparatus 1 is still satisfactory.
FIG. 2 is a schematic view illustrating a first test image file for performing the print testing operation by the inkjet printing apparatus according to the prior art. The first test image file T comprises multiple first blocks b11˜bnn. The interval between every two adjacent first blocks is equal. For example, the first block b11 and the first block b12 are distant from each other by a first block interval D1. The first block b12 and the first block b13 are distant from each other by another first block interval D2. The first block b11 and the first block b21 are distant from each other by another first block interval D3. The first block interval D1, the first block interval D2 and the first block interval D3 are equal. Due to many factors adversely affecting to the inkjet printing apparatus 1, the intervals between adjacent physical blocks of the print test pattern are possibly unequal. For example, if the surface of the moving shaft of the transmission mechanism 11, which is disposed along the printing direction X, is not flat, the transmission mechanism 11 will be moved at inconsistent speeds during the printing operation of the inkjet printing apparatus 1. Under this circumstance, the print test pattern is erroneous.
For correcting the inkjet printing apparatus 1 and increasing the inkjet accuracy, the print test pattern is then scanned by an image scanner in order to obtain a second test image file. Similarly, the second test image file includes multiple second blocks. Every two adjacent first blocks are distant from each other by a second block interval. The positions and the intervals of the second blocks included in the second test image file are identical to those of the physical blocks included in the print test pattern. Next, the second block intervals of the second test image file are accumulated and an average value of the accumulated second block intervals is calculated. The average value is compared with the first block interval (e.g. D1) of the first test image file T. According to the comparing result, the timing of ejecting the ink of the inkjet printing apparatus 1 is adjusted. After adjustment, the intervals between adjacent physical blocks of the print test pattern are equal to the average value.
Although the conventional printing correction method is effective to adjust the equal intervals of the physical blocks, there are still some drawbacks. For example, in comparison with the first test image file T, all blocks included in the adjusted print test pattern are slightly shifted. In other words, the images printed by the corrected inkjet printing apparatus 1 are somewhat distorted.
Therefore, there is a need of providing an inkjet printing correction method for obtaining a non-distorted image so as to obviate the drawbacks encountered from the prior art.